A cylindrical sliding bearing is composed of assembled two half bearings and has been conventionally used as a sliding bearing for a journal or a crankpin portion of a crankshaft of an internal combustion engine. In order to feed lubricant oil to the sliding bearing, the oil is first fed from outside of the sliding bearing for a journal portion into an oil groove on an inner circumferential surface of the sliding bearing, and then fed to a sliding surface of the sliding bearing for a journal portion. The oil is then passes through an inner oil path of the crankshaft and fed to a sliding surface of a sliding bearing for a crankpin portion (for example, see JP-A-08-277831).
In the conventional sliding bearing for a journal portion or a crankpin portion of a crankshaft, a crush relief is formed on an inner circumferential surface of a half bearing. Although displacement or deformation may generate when end surfaces of a pair of half bearings are butt to assemble the half bearings into a bearing housing, the displacement or deformation are absorbed due to the crush relief. In the specification, the term “crush relief” means a region close to a circumferential end surface of a half bearing and having reduced wall thickness gradually reducing toward the circumferential end surface. The center of curvature of a bearing inner circumferential surface in the region with reduced wall thickness is different from that of a bearing inner circumferential surface in another region, as defined in SAE J506 (see items 3.26 and 6.4), DIN1497 (see section 3.2), and JIS D3102 (see item 2.4).
There has been also proposed a sliding bearing where not only the crush relief but also a chamfer is formed at a circumferential end portion of an inner circumferential surface of a half bearing such that a foreign substance is discharged through a gap between the crush relief and a crankshaft surface as well as between the chamfer and the crankshaft surface to prevent the foreign substance in oil to be fed to the sliding bearing from being supplied onto a sliding surface of the sliding bearing (for example, see JP-A-2005-69283).